I remember the excitement of seeing a heron, large, grey and graceful, wings rising and falling as it escaped along a river beneath a canopy of trees. It didn’t want to be near us, because we were people. In later years we would occasionally see one stock still on the far side of a lake, close to the reeds of a nature reserve where no man could tread. The impression was of a creature wild and shy, and if it cleared out your fish pond, it would work unseen at dawn.

The idea of a heron near the River Thames would have been laughable, not only because the birds shunned human company, but because there was nothing edible in the water. Hammersmith and Chiswick were fishing villages in the eighteenth century, but the advent of the flush toilet finished that activity. I shall leave you to imagine why. As the Metropolitan Board of Works won a heroic battle in the interests of hygiene, so the waters of the Thames were taken over by industrial effluent, oil, and paint, and the fish wisely stayed away.

Late in the twentieth century the river became genuinely clean, and creatures returned to live there. The villages were engulfed by the spread of London, but had gained rather than lost in charm, and the heron returned. One stands on a houseboat roof by Hammersmith Bridge, neck folded like a teapot spout. Another can be seen flapping over the gravel at Barnes. A tame heron supervises those who feed the ducks and swans at Richmond. I have never seen the heron eat a piece of bread; but it stands aloof at the edge of a crowd of feeding birds, with no fear of the humans a few feet away.

Tamest of the tame is the heron in the grounds of Chiswick House, a delightful classical villa once described as ‘Too small to live in, and too big to hang to a watch.’ The park is a place of beauty, well worth a visit. I stand on a hump-backed bridge over the lake, watching a local man reaching into his Sainsbury’s bag for bread for the waterfowl. The heron stands beside the fence, appearing to identify more with the human than the birds. When the supply is finished, and the man joins me on the crown of the bridge, the heron hoists himself into the sky and lands on the parapet three feet away, staring at us impassively for a while before launching into a semi circle and landing on our other side, apparently expecting one of us to produce a fish.

It may no longer be rare to see a heron, but there’s still something memorable about the experience.